Scroll machines, such as scroll compressors using a fixed scroll and an orbiting scroll, are well known in the industry. Each of the scrolls of a scroll compressor has a spiral wrap extending axially from a base plate. The spiral wraps nest with one another to form pockets of varying volume. A fluid introduced into a low pressure area of the pockets is compressed by the cooperating movement of the spiral wraps, and discharged from a high pressure area proximate the center of the wraps. A motor drives a crankshaft which in turn drives the orbiting scroll along its orbital path. A rotation prevention mechanism, such as an Oldham coupling, is used to prevent rotation of the orbiting scroll as it undergoes such orbital motion.
Scroll-type compressors, as well as other types of scroll machines, may experience high pressure differential loads which can exceed their design capabilities and lead to failures unless protected by a suitable pressure relieving device. Scroll machines need to be protected against high pressure ratio conditions as well. High pressure ratio conditions may occur during loss of charge and result in a high temperature rise in the compressor pump. This in turn may cause a range of failure modes, including tip and floor scoring. High pressure ratios can also induce a wobble instability in the orbiting scroll, which could lead to failure.
A pressure ratio limiting device for a scroll machine is shown in U.S. Pat. No. 5,169,294 to Barito. This device operates to pass fluid at discharge pressure back to the suction pressure portion of the scroll housing when the pressure ratio exceeds a predetermined value, but will not prevent the buildup of excessive pressure differential.
U.S. Pat. No. Re 35,216 to Anderson et al. discloses a scroll machine having a valve which passes discharge pressure fluid to the suction pressure portion of the housing when the pressure ratio exceeds a predetermined value. The valve of Anderson et al has seals formed between one of its scrolls and another member of the compressor.
U.S. Pat. No. 5,527,158 to Ramsey et al. discloses a scroll machine having a valve which passes discharge gas when a sensed pressure exceeds a predetermined value. The device of Ramsey et al does not respond to excess pressure differentials or excess pressure ratios.
It is an object of the present invention to provide a pressure relief device which reduces or wholly overcomes some or all of the aforesaid difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain preferred embodiments.